Defending Evolution from ID Distortions

Posts tagged “Genes

Evolution, Mutation and Misconceptions

A common objection to the Evolutionary model is the idea that Mutations are a driving force for change. It is seen all over Creationist literature that mutations destroy information, and never add anything, or have any benefits. — For example, the Muslim Creationist Harun Yahya claims,

The direct effect of mutations is harmful. The changes effected by mutations can only be like those experienced by people in Hiroshima, Nagasaki, and Chernobyl: that is, death, disability, and sickness. […] Not surprisingly, no useful mutation has been so far observed. All mutations have proved to be harmful. (The Evolution Deceit, page 55)

A few months ago, while I was debating with a creationist, I found myself having to correct a major misunderstanding he had. He repeated an argument  about Natural Selection, saying that Natural Selection is not the same as Evolution because it produces nothing new. It just “selects'” — As soon as he said this, I remembered hearing the same thing from a Kent Hovind debate. 

As soon as he said that, I quickly corrected him. Nobody says that Natural Selection “creates” anything new. When I took History of Life in Biology, that was one of the things I was taught: “Natural Selection doesn’t create new traits.” Mutations create new traits, and natural selection then determines if the new trait is favorable or good enough for a living organism to survive in a certain enviroment.  — He then interrupted saying, “Mutations are always harmful!” When I corrected him on that, he then said, “Well, cancer is a mutation! . . So, you’re telling me that if we get a whole population with cancer — “ At that, I kept repeating myself that wasn’t what I was saying and told him to stop attacking a strawman.

 He then defied me to name one beneficial mutation, just one. At that, I gave the (probably over cited) anti-bacterial resistance. He then said that didn’t count because the bacteria didn’t pass on the newly acquired resistence to its descendants, and the new traits have to be heritable. — But Creationists who make that claim are demonstrably wrong. The fact is that newly resistant bacteria do pass on their newly acquired resistance to new generations. I also pointed out the evolution of the HIV virus -the “ultimate evolver”- which didn’t seem to  make even the slightest dent, as if I expected it to.

One often cited case of a beneficial mutation is the sickle-cell anemia. Kent Hovind, in a debate with Michael Shermer, mocked this example by comparing it to being beneficial in the sence of cutting off your feet so you do not get athlete’s foot. — But it’s not so simple. Kent Hovind apparently is ignorant of the qualifiers that determine whether or not the sickle-cell mutation is beneficial or not. If the mutation is in the heterozygous state, then the mutation is detrimental causing disease and early death. However, if the mutation is heterozygous, then that causes its carriers to be resistent to infection and malaria.

One really famous example of a beneficial mutation is the CCR5-Delta 32. This mutation occurs in chromosome three in the human genome. Individuals that carry this particular mutation are resistent to the HIV virus. The heterozygous variant of this mutation is able to slow down the progression of the HIV virus while the homozygous version of the mutation causes immunity to the virus. — It is obvious that the claim made by Harun Yahya in his writings is wrong. There are several examples of beneficial mutations. It has even gotten to the point that some Creationists now admit that they in fact exist, but they then try to put qualifiers on it.

Anyway, now that Creationists have accepted that mutations can be beneficial, they now changed tactics in order to salvage their ever evolving creation model. — One creationist from CMI, while talking about the CCR5-Delta 32, tries to work his way out by saying,

However, it clashes irreconcilably with the evolutionary view that the accumulation of mutations over time brings about upward evolution (increasing functional complexity).

 . . . And then later, he then cites a paper from Nature which mentions a downside to this particular mutation. The implication he seems to be trying to give is that because it can be associated with primary sclerosing cholangitis, then therefore it cannot be count as evidence. — Creationists make similar claims about antibiotic resistence of bacteria, saying that these mutations lead to a “loss of function.”

What these excuses show is a lack of understanding of how Evolution works with mutations. As I have already pointed out in a previous post, evolution doesn’t necessarily lead to increased complexity, though it may. But there is no pre-ordained goal. All that matters is if the change is heritable, and if it is, then that works as evolutionary change. — Also, no one has ever said that mutations that lead to evolutionary change cannot have a downside. There will always be a downside. What matters is if the variation is beneficial or good enough to survive in a certain environment. In an enviroment where there is plenty of AIDS, the CCR5-Delta 32 mutation would be beneficial. Natural Selection will favor those particular individuals that carry it.

Finally, there is Gene Duplication. I know that Creationists would love to pounce on this example and say “It’s just duplicated information.” — I wonder if these same Creationists would be interested in the fact that over 97% of human genes are duplicates. Anyway, gene duplication offers raw material for Evolution and mutation, though it is true that high rates of duplication often lead to high rates of gene loss also, (a fact that would be useless for Creationists to hijack for reasons mentioned above.) What happens is, a gene gets duplicated, and then the duplicate copy has no selection pressures, so it is now free to evolve and mutate on its own, though the gene doesn’t always survive.  

I’m sure that Creationists would love to object to new function ever being derived from duplicated genes, but the fact is that it does happen. A good example is the Eosinophil Cationic Protein (or the ECP) which is toxic to bacteria by making their cell mambranes porus. Also, it is useful in the management of Asthma, despite it’s limitations. — Then there is the Eosinophil-Derived Neurotoxin (the EDN) which helps to prevent viral infections, though it’s accumulation in the intestine is associated with tissue loss.

Furthermore, observations in the genomes of bacteria only aid the conclusion that gene duplication is a viable mechanism for Evolutionary change, as the divergence of duplicated enzymes seems to have been a main contributor -though not no only one-  to the causation of new species of bacterium.

One need not be a geneticist to research the claims of anti-evolutionists to come to the realization that almost everything they claim about mutations is spurious. Even though it is true that most mutations are harmful, it is also true that in certain environments some can be quite beneficial in which cases natural selection will favor them. Some gene duplicates also show neofunction completely debunking the idea that nothing new arises from mutation.

References:
Evolution and Disease, from ChemHeritage.org
Genetics Demystified, page 151. By Edward Willett
Beneficial Mutation, by Ningthoujam Sandhyarani. From Buzzle.com
Beneficial Mutations, from SkepticWiki.
Examples of Beneficial Mutations in Humans, from The Evolution Evidence Page.
Almost all human genes resulted from ancient duplication, by Roy J. Britten, from the Proceedings of the National Academy of Sciences.
Gene Duplication and Evolution of Gene Function, from Evolution and Developement Group.
Evolution by Gene Duplication, by Jianzhi Zhang, from TRENDS in Ecology and Evolution. Also see Positive Darwinian Selection after gene duplication in primate ribonuclease genes, by Jianzhi Zhang, Helene F. Rosenberg, and Masatoshi Nei, from the Proceedings of the National Academy of Sciences.
Eosinophil cationic protein: Is it useful in asthma? A systematic review, by Gerald C.-H. Koha, Lynette P.-C. Shekb, Daniel Y.-T. Gohb, Hugo Van Beverb, David S.-Q. Koha.
Eosinophil Derived Beurotoxin (EDN)
Evolution by leaps: gene duplication in bacteria, by Margrethe H Serres, Alastair RW Kerr, Thomas J McCormack, and Monica Riley. From Biology Direct.